Coleman regenerative engine with exhaust gas water extraction

ABSTRACT

An improved turbine engine topology, wherein the improvement comprises a repositioning, with respect to a conventional intercooled regenerative turbine engine topology, of exhaust gas output from a low pressure turbine stage to a regenerator, to an exhaust gas output from a high pressure turbine stage to the regenerator. The engine topology may additionally employ, as an intermediate stage between the high pressure turbine and the low pressure turbine, a feedback control system, whereby the exhaust gas output from the high pressure turbine stage to the regenerator flows through the feedback control. The engine topology may advantageously also employ an additional cooler and an additional exhaust gas output in the feedback control, whereby exhaust gas flows from the feedback control through the additional cooler to a high pressure compressor stage, or the exhaust gas can flow from the feedback control through a bottoming cycle to the high pressure compressor stage. An exhaust gas condenser may advantageously be placed into the bottoming cycle system. The bottoming cycle/condenser improvements may alternatively be effected an other wise conventional intercooled regenerative turbine engine topology.

This application is a Divisional of Ser. No. 09/970,032, filed Oct. 2,2001, now issued as U.S. Pat. No. 6,651,421 issued Nov. 25, 2003, whichclaims priority to U.S. Provisional Patent Ser. No. 60/237,558 filedOct. 2, 2000.

TECHNICAL FIELD

The invention relates to the field of gas turbine engines and to thefield of power generation and to water reclamation; more particularly,it relates to method and apparatus for a gas turbine regenerative enginewith exhaust gas water extraction.

BACKGROUND OF THE INVENTION

Variations of Gas Turbines

There are many variations on simple cycle gas turbines. Each offerssomething special, be it operating economies or features that meetspecific needs. The features might be small size, lightness in weight,high reliability, simplicity, or another measurable attribute. Emphasisis often placed on performance and power density, and achieving theseobjectives through use of known technologies and sound design principlesfor compressors, turbines, combustors, heat exchangers, and technologyfrom related conventional materials sciences would be desirable. It isexpected that achieving large gains requires the component arrangementto be new and different, to depart significantly from conventionaldesigns. Any departure that results in an increase in complexity alsohas to significantly improve performance to be commercially useful; themore the departure, the more attractive the gains have to be.

Without question, component research and development efforts over recentyears have served well to define advanced levels of aerodynamic andthermodynamic component efficiency. By combining these advances withsimilar gains in materials sciences and cooling technologies, capabilitynow exists to design for high stage pressure ratios and high operatingtemperatures. But adopting an approach that would capture the full rangeof these advances would be very costly and would involve undesirablyhigh risks. What is needed are the benefits to be derived from a newflow-path arrangement, rather than high stage loadings, hightemperatures, and high stresses.

Fundamental Combustion Characteristics of Fuels.

For most gaseous fuels, the products of complete combustion are carbondioxide and water (in the form of water vapor). Depending on content,small amounts of sulphur dioxide can be produced, along with othergaseous products. However, the most significant products of combustion,by far, will be carbon dioxide and water. The rest, for the purpose ofthis discussion, can be ignored. The most important fundamental resultis that for every pound of fuel burned, in combination with the ambientair used to support combustion, the gases produced will contain as muchas 2.25 pounds of water vapor and up to 2.75 pounds of carbon dioxide.Until now, it does not appear that any attention has been given torecovering any of the products of this combustion, let alone recovery ofthe exhaust water. Fruitful human endeavors have always depended upon areadily available water supply. What is desirable, and what would bedifferent from any other power producing system, is a power producingsystem from which exhaust gas water may readily be recovered. What isneeded is a source of water that generates power efficiently,particularly in drought-ridden areas or desert regions; what is neededis an engine design for applications in developing regions that need twovital commodities: water and power. What is needed is a design that isindependent of geographical location, climate, or changingmeteorological conditions, but which does not have a negative impact onother engine favorable operating characteristics.

DISCLOSURE OF THE INVENTION

What is disclosed is an engine design for applications in developingregions that need two vital commodities: water and power.

The benefits disclosed herein are derived as follows:

-   -   A. First, only flow path arrangements that will enhance        thermodynamic capability without depending on new,        high-temperature technologies are considered. If high stage        pressure ratios are not absolutely needed to achieve high cycle        efficiency, then another way to get more power and better        efficiency for the same size is to be employed.    -   B. Any special advantages to using heat exchangers such as        regenerators or intercoolers in a new flow path are considered        with a view toward achieving gains in efficiency (especially        fuel saving) that outweigh any added complexity of incorporating        the coolers into any new flow path.    -   C. Use of a bottoming cycle to augment output power is        considered as well, especially as to whether it yields enough        improvement, and how best to incorporate a bottoming cycle into        the new system.

The resulting system disclosed is designed to fill a dual need; that is,provide a source of water while generating power efficiently. The flowpath arrangement has been tailored to accomplish both. In that sense,the configuration is quite different from conventional through-flowdesigns; however, the components are well within known capabilities. Thesame is true for the heat exchangers (regenerators and coolers) and forelements of the bottoming cycle disclosed herein as well.

In simple terms, a bottoming cycle to increase thermodynamic efficiency,and a condensing unit to recover water from the products of combustionare preferably added to a basic but novel controlled feedbackregenerative turbine engine, also referred to herein as the regenerativeengine. The resulting configuration is unique in that it can deliverpower efficiently while producing significant amounts of potable water,features that can be a priceless combination in drought-ridden areas ordesert regions.

The core of the disclosed power/water system is the novel regenerativeengine. This engine is based on well-established technologies related tosuccessful turbine engines. But the novel regenerative engine differsfrom others in production in that the flow path is tailored to maximizeefficiency and output power well beyond conventional practice. Forexample, fuel consumption rate of a disclosed regenerative engine is atleast 10 percent lower than that of a conventional diesel engine, whilespecific power is roughly twice that of the most advanced turbineengine. The novel flow path for such an engine may be seen in FIG. 2.

An improved turbine engine topology is disclosed, wherein theimprovement comprises a repositioning, with respect to a conventionalintercooled regenerative turbine engine topology, of exhaust gas outputfrom a low pressure turbine stage to a regenerator, to an exhaust gasoutput from a high pressure turbine stage to the regenerator. The enginetopology may additionally employ, as an intermediate stage between thehigh pressure turbine and the low pressure turbine, a feedback controlsystem, whereby the exhaust gas output from the high pressure turbinestage to the regenerator flows through the feedback control. The enginetopology may advantageously also employ an additional cooler and anadditional exhaust gas output in the feedback control, whereby exhaustgas flows from the feedback control through the additional cooler to ahigh pressure compressor stage, or the exhaust gas can flow from thefeedback control through a bottoming cycle to the high pressurecompressor stage. An exhaust gas condenser may advantageously be placedinto the bottoming cycle system. The bottoming cycle/condenserimprovements may alternatively be effected an other wise conventionalintercooled regenerative turbine engine topology.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of the novel regenerative feedback engine withbottoming cycle and exhaust gas condensation.

FIG. 2 is a schematic of an alternate embodiment of the novelregenerative feedback engine.

FIG. 3 is a schematic of a conventional simple cycle engine.

FIG. 4 is a schematic of a conventional regenerative engine.

FIG. 5 is a schematic of a conventional intercooled regenerative engine.

FIG. 6 is a graph of fuel consumption comparisons.

FIG. 7 is a flow chart depicting the evolution of the system of theinvention.

FIG. 8 is a schematic of the engine of FIG. 2 with the cooler replacedschematically by a bottoming cycle.

FIG. 9 is a schematic of a bottoming cycle.

FIG. 10 is a graph of fuel consumption comparisons showing the additionof the bottoming cycle.

FIG. 11 is the schematic of FIG. 9 showing replacement of the F85condenser.

FIG. 12 is a schematic of the combined bottoming cycle and watercondensing system of FIG. 1.

BEST MODE OF CARRYING OUT THE INVENTION

The system may be optimally sized for roughly 10,000 KW for each unit,but a unit can be sized to accommodate particular user recommendationsand needs. The concept does not generally change with size. Size mightwell be chosen to promote design for mass production of units that canbe interchanged easily to facilitate maintenance or permittransportability from one region to another within a power grid. Equallyimportant, the size choices can also facilitate application to wideareas of market interest.

Components

Conventional components are, for the most part, all that is needed.Preferred compressors are well within the state-of-the-art, with someengineering required only for matching and for variations in flow;anticipated stage pressure ratios are well within current practiceparameters. Turbines are also well within state-of-the-art, withoperating temperatures well below levels that might otherwise requirespecial cooling, with engineering only required to accommodatevariations in flow. Stage loading is also well within current practice,and no new exotic materials are needed, and no introduction of hightemperature is required.

Preferred combustors require some engineering to accommodate flowvariations in the system. A preferred regenerator is located in a highdensity flow path, resulting in small size while transferring heateffectively, and significantly lowering volume compared to traditionaldesigns. Preferred intercoolers encounter no known barriers.

A preferred bottoming cycle uses F-85 organic fluid in a closed loop; noproblems with use in conventional heat exchangers or turbines areexpected. A preferred condensing system combines with a bottoming cycleto remove water from gases at high pressure. Condensing system size isminimized by high density environment.

Turning now to the drawings, the invention will be described in apreferred embodiment It may be seen from FIG. 2 that the flow path isquite different when compared to familiar and simpler conventionalturbojet and turboshaft engines shown in FIG. 3, and is characterized bya more complex arrangement of components. In FIG. 3, the flow pathsthrough the simplest of turbine engine arrangements may be seen. Thissystem is a through-flow, simple cycle gas turbine engine. Compressorsprovide the high pressure ratio required, and fuel is burned to raisethe energy level so that the turbines can provide enough power to drivethe compressors and the output shaft. In this illustration, shaft poweris extracted, rather than jet thrust. For the sake of maximizing fuelefficiency, this conventional system demands a cycle that operates athigh pressure ratios and high temperatures, both of which requirecontinual advances in technology, resulting in costly research.

For example, the push toward high temperature operation requiresexpensive cooling techniques to avoid exceeding material limits.Temperatures in a high output version of the system illustrated in FIG.3 can be above 2500 F, which is at or near the melting points of specialalloys. The extreme measures adopted to deal with high temperatures haveintroduced hidden complexities and concerns for high initial costs andpotentially expensive maintenance procedures. At the same time, the pushtoward better fuel economy has required that higher pressure ratio beprovided by fewer stages, resulting in highly sensitive aerodynamic andthermodynamic designs that are subjected to high stresses and morecritical matching requirements. Regardless of component advances,inherent inefficiencies at most partial-power conditions continue to beshortcomings of the engine arrangement illustrated in FIG. 3. Althoughthe flow path has earned the name Simple Cycle, the constant push to dobetter has forced research into new technology areas that will continueto drive costs upward in ways that are anything by ‘simple’.

In part, to address the concern for better fuel consumption, theregenerative (or recuperative) engine cycle (FIG. 4) was introduced.Exhaust energy is recovered by using at least a portion of the exhaustgas to heat air discharged from the compressors before adding fuel inthe combustor. This approach adds a heat exchanger before fullyexhausting the hot gases. Without question, this improved arrangementsaves fuel; however, it requires extreme care in design to minimizepressure losses and to avoid increasing back pressure, both of whichhave a significant negative impact on performance. In addition, theseperformance considerations lead designers toward very large heatexchangers to minimize flow restrictions and maximize heat transfer.

Another approach to minimizing fuel consumption is to increase theoverall pressure ratio without increasing the amount of work required todrive the compressors. The system illustrated in FIG. 5 cools the airbefore compressing it as a means of further increasing its density.Cooling the incoming ambient air is thought to introduce intolerablelosses, but placing a heat exchanger between compressor stages is themost convenient and the most profitable. This arrangement, with coolingbetween compressor stages, has become known as intercooling. When thisflow path is combined with that of the regenerative engine, the resultis the intercooled regenerative configuration of FIG. 5, andincorporates the fuel saving features of each. These conclusions arewidely accepted and have been used in applications where fuel economy isthe more significantly driving factor than size and/or weight of theequipment. In most aircraft applications, for example, these approachesprobably never would be considered. However, for stationary power plantsor some large vehicles (such as ships or locomotives), the arrangementbecomes a highly acceptable choice. The fuel saving is more than worththe cost of added equipment or increase in complexity. In any case, itis clear that the simple cycle engine, by itself, is most preferred forits basic simplicity. It is recognized that some of that simplicity mustbe sacrificed to achieve significant gains in performance.

The regenerator has two inherent disadvantages. One is that its locationat the engine exhaust places it in an area where discharge to ambientpressure (and at much lower relative air density) requires a very largeheat exchanger for best high heat transfer effectiveness. The seconddisadvantage is that a higher gas temperature is needed to enhancetransfer of relatively more heat to the air before it enters thecombustor. What is needed is a relocation of the regenerator to an areamore conducive to transferring heat and to reducing size. What is nowdisclosed is that by recirculating hot gases from between the turbinestages, two significant gains can be made. First, size of theregenerator can be reduced enormously (better than 5:1) and the heattransfer is improved because of the more favorable conditions. Inimproving the conventional intercooled recuperated engine cycle (SeeFIG. 5), the intercooler is advantageously left unchanged, as thepotential for large improvements in performance can readily be met withjust the relocation of the regenerator.

Optimalization of amount of recirculation, the most reasonablethermodynamic balance of temperatures and pressure ratios, and systemfuel and gas flow control requirements is effected by a feed-backcontrol that is synchronized with fuel and power settings. In addition,component performance capabilities in a variable flow environment arealso desirable optimized to enhance aerothermodynamic matching. Thusrequired performance standards can be met without the need to rely onadvanced technology components, and so a turbine operating temperatureis chosen that does not require either internal blade cooling or stagepressure ratios that might demand extensive development testing.

These advantages of the disclosed regenerative feedback engine (FIG. 2),combined with a requirement for good fuel economy throughout the entireoperating range, outweighs any concerns about increase in complexity.Fuel consumption comparisons of the regenerative engine with hightechnology gas turbines and modern Diesel engines is shown in FIG. 6.The novel regenerative engine of FIG. 2. has superior potential in thepart-power region, where the vast majority of engines operate most ofthe time. In particular, performance and operating time below 60 percentpower are of major interest in nearly all vehicle and stationarysystems. The relative flatness of the fuel consumption rate throughoutis unique and unmatched by other more familiar engine types.

It was most encouraging to learn that the concept did not requireturbine temperatures above 2200 F, at a point in time when other turbineengines were being designed for operation at much higher levels.Compressor stage pressure ratios also do not need to be above 6:1, whichis well under the values required for other gas turbines. Because of therecirculation, flow-path arrangement, and component locations, theoutput power for a given amount of inlet airflow was found to be farabove that of other engines designs. High technology gas turbines mightreach 250 HP for each pound of air used, while the novel regenerativeengine disclosed exceeds 600 HP per pound of air. This is widelyregarded as a most important measure of power versus physical size.

A summary of the development of the novel regenerative engine, thoughseveral conventional stages, to the novel rearrangement of the flow ofthe regenerative exhaust gases, and then onward to additional featuresadded to achieve the disclosed optimized water extraction powerproducing engine, is shown in FIG. 7. The path followed to arrive at thenovel design starts with the turboshaft/turbojet, and progresses throughregenerative, and intercooled versions.

The novel regenerative engine (FIG. 2) differs from conventional designsin that the component arrangement and flow path permit a dramaticincrease in specific power and power density, making it more thancompetitive in size (at least 2:1 better) when compared to the mostcompact engines that have so far been developed. The combination permitscontrol of feedback flow that can be tailored in the recirculation loopto meet power demands. This configuration introduces a new capability toaugment power output while minimizing fuel consumption (flattens thespecific fuel consumption curve) over a much broader range of power thanany other turbine engine concept. In another size-related area, the hightemperature and high density gases in the regenerator provide a uniqueopportunity to transfer beat effectively while reducing volume by about7:1 (compared to conventional designs where such devices are located atthe engine exhaust). Taken together, these features result in an enginewith performance and size characteristics unmatched in the industry, butat some increase in complexity. It will be appreciated however thatthere will be many applications where the economic advantages will faroutweigh the complexity.

The invention is directed primarily at making big gains in fuel economy,while holding to the importance of increasing specific power. In review,it will be noted that the conventional regenerative engine, by itself(FIG. 4), could reduce fuel consumption, but not without some penalty inoutput power and engine size. Adding the intercooler (FIG. 5) served tofurther improve fuel economy and can increase output power at the sametime, but it also increases engine weight and size. Regardless of theseconventional choices, the fundamental simplicity of the simple cycle hasto be sacrificed to effect a major change in performance, weight, orsize.

But can the novel regenerative feedback engine (FIG. 2) also be furtherimproved in this regard? Could even greater and more compellingimprovements be introduced to offset any added complexity? That questionled to addressing a bottoming cycle as a means to further augment outputpower and fuel economy. A closed loop (FIGS. 8 & 9) is added to replacethe feedback cooler of the FIG. 2 design. This addition has the benefitof augmenting power and reducing fuel consumption by another 10 to 12percent, certainly worth considering in any power plant. A preferredfluid for the closed circuit of the bottoming cycle can be expanded to agaseous state, used to drive a turbine, condensed, cooled, and againexpanded within the thermodynamic boundaries of the feedback cooler. Anpreferred organic fluid, F85, fits these needs. By means of astraightforward combiner gear, the power output of the bottoming cyclesaugments the output of the basic novel regenerative engine. While abottoming cycle is not a new idea, adapting it to the design shown inFIG. 2 represents more than just offsetting some previously-notedcomplexity. The novel regenerative engine, even with just the additionof a bottoming cycle, represents a much desired step ahead in size andperformance attributes that are not available in any other engine. Theresulting fuel consumption, shown in FIG. 10, indicates the level ofexpected performance improvement.

If the water in the products of combustion is also recovered however,the engine then fills the critical requirement of promoting developmentof many areas of the globe where water is at least as crucial orunavailable as the power to be produced from the engine. The payoff canbe enormous, especially in areas that have readily available, abundantfuel reserves (gas or oil) but would, otherwise, remain uninhabited forlack of water and power. A preferred location in the flow path toprecipitate the water with least operating loss is shown in FIGS. 11 &12. A preferred location is in the bottoming cycle, using a secondcondenser. In FIG. 12 hot gases from the regenerative engine are passedthrough a cooling and condensing tank where water is precipitated andcollected. The cooled gases are returned to the engine cycle (inparticular, to the High-Pressure Compressor stage). Cooling is providedby a precooler that advantageously uses an ambient air heat exchangerand a liquid coolant heat exchanger, which is advantageously part of abottoming cycle.

With regard to systems and components above referred to, but nototherwise specified or described in detail herein, the workings andspecifications of such systems and components and the manner in whichthey may be made or assembled or used, both cooperatively with eachother and with the other elements of the invention described herein toeffect the purposes herein disclosed, are all believed to be well withinthe knowledge of those skilled in the art. No concerted attempt torepeat here what is generally known to the artisan has therefore beenmade.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural features. It is to beunderstood, however, that the invention is not limited to the specificfeatures shown, since the means and construction shown comprisepreferred forms of putting the invention into effect. The invention is,therefore, claimed in any of its forms or modifications within thelegitimate and valid scope of the appended claims, appropriatelyinterpreted in accordance with the doctrine of equivalents.

1. A turbine engine system comprising a compressor stage having low andhigh pressure compressors, a turbine stage having high and low pressureturbines, and a regenerator, wherein an exhaust gas output from the highpressure turbine flows to the regenerator before returning to the lowpressure turbine.
 2. The engine system of claim 1 further comprising, asan intermediate stage between the high pressure turbine and the lowpressure turbine, a feedback control system, whereby the exhaust gasoutput from the high pressure turbine stage to the regenerator flowsthrough the feedback control.
 3. The engine system of claim 2 furthercomprising an additional cooler and an additional exhaust gas output inthe feedback control, whereby exhaust gas flows from the feedbackcontrol through the additional cooler to the high pressure compressorstage.
 4. The engine system of claim 2 further comprising a bottomingcycle system and an additional exhaust gas output in the feedbackcontrol, whereby exhaust gas flows from the feedback control through thebottoming cycle to the high pressure compressor stage.
 5. The enginesystem of claim 4 further comprising, in the bottoming cycle system, anexhaust gas condenser.
 6. In a conventional intercooled regenerativeturbine engine system, the improvement comprising a bottoming cyclesystem whereby exhaust gas flows from a high pressure turbine stagethrough the bottoming cycle to a high pressure compressor stage.
 7. Theengine system of claim 6 further comprising, in the bottoming cyclesystem, an exhaust gas condenser.
 8. The engine system of claim 6wherein the bottoming cycle is further comprised of an organic fluidclosed loop and a bottoming turbine.
 9. The engine system of claim 8wherein the turbine exhaust gas flows through a heat exchanger in thebottoming cycle and thereby transfers heat to the organic fluid closedloop.
 10. A turbine engine system comprising a compressor stage havinglow and high pressure compressors, a turbine stage having high and lowpressure turbines, and a regenerator, wherein an exhaust gas output fromthe high pressure turbine flows to the regenerator a through feedbackcontrol system before returning to the low pressure turbine.
 11. Theengine system of claim 10 further comprising an additional cooler and anadditional exhaust gas output in the feedback control, whereby exhaustgas flows from the feedback control through the additional cooler to thehigh pressure compressor stage.
 12. The engine system of claim 11further comprising a bottoming cycle system, wherein the cooler and anadditional exhaust gas output in the feedback control are part of thebottoming cycle system, whereby exhaust gas flows from the feedbackcontrol through the bottoming cycle to the high pressure compressorstage.
 13. The engine system of claim 12 further comprising, in thebottoming cycle system, an exhaust gas condenser.
 14. The engine systemof claim 10 further comprising a bottoming cycle system and anadditional exhaust gas output in the feedback control, whereby exhaustgas flows from the feedback control through the bottoming cycle to thehigh pressure compressor stage.
 15. The engine system of claim 14further comprising, in the bottoming cycle system, an exhaust gascondenser.
 16. The engine system of claim 14 further comprising, in thebottoming cycle system, an exhaust gas condenser and an organic fluidclosed loop with fluid cooler, wherein the exhaust gas condenser and theorganic fluid cooler are combined by running a cooled organic fluid loopfrom the cooler through the exhaust gas condenser to absorb heat fromthe exhaust gases.
 17. The engine system of claim 16 further comprising,in the bottoming cycle system exhaust gas condenser, a cooling air loopfrom the fluid cooler that passes through the exhaust gas condenser topre-cool exhaust gases before they pass through the cooled organic fluidloop in the condenser.